Normally, various taxiways are laid in an airport for permitting aircraft to taxi from one place to another, and it is essential to determine where in these taxiways each aircraft is currently located.
By accurately determining the location of each aircraft in the taxiways, the aircraft on the taxiways can be effectively guided, and collision of the aircraft on the taxiways can be avoided.
As methods for determining the locations of aircraft in an airport or the like, there are known
(1) the method of visually determining the locations of aircraft by a number of personnel monitoring the aircraft either directly with their own eyes or by using ITVs; and PA1 (2) the method of determining the locations of aircraft according to the outputs of sensors placed along the taxiways.
However, since an airport typically consists of a vast area and each of the taxiways extends a substantial distance, a large number of personnel are required for visually monitoring aircraft either directly with their own eyes or by using ITVs, and the need for human intervention does not allow total elimination of the possibility of accidents due to human errors.
When a number of sensors are to be arranged along taxiways, the number of the sensors must be adequate and they must be wisely arranged in proper locations for them to be effective in accurately determining the positions of aircraft. However, there is a limit to the locations where such sensors can be installed, and the cost will be prohibitively high when a large number of sensors are to be placed in a large number of locations.